This invention relates generally to semiconductor devices of the resin-seal type and more particularly to the surface structures of semiconductor pellets of large areas.
A resin-seal type semiconductor device is fabricated by mounting a semiconductor pellet on a lead frame, carrying out wire bonding, and thereafter sealing the device with a synthetic resin such as an epoxy resin.
A typical known semiconductor device of resin-seal type in pellet form, as will be described more fully hereinafter, comprises a silicon substrate, a field oxide film formed on the substrate and surrounding an element region, a MOS transistor, for example formed on the element region, an interlayer insulation film disposed over the field oxide film, a wiring layer extended from the element region, a bonding pad part 5 for connection to the wiring layer, which together with the wiring layer is formed on the layer insulation film, and a passivation film deposited on the upper surface of the structure except for a bonding pad window formed in the part of the passivation film correspondingly above the bonding pad part.
In a conventional device of the above described structure certain parts thereof are subjected to stress by the sealing resin as a consequence of sudden variations in the surrounding temperature. Consequently, cracks readily develop in such parts, whereby moisture resistance is lost. Furthermore, problems such as deformation in the wiring layer below the passivation film, and even wire breakage, occur together with cracking. A further problem is the propagation of the cracks to the layer insulation film and the field oxide film, which gives rise to further problems such as lowering of the semiconductor device performance and a drop in the yield during production thereof.